In a mobile communication system that switches a base station, with which a mobile terminal communicates in a cell boundary, from a first base station to a second base station according to handover control, the mobile terminal notifies assignment information on a radio resource assigned by the first base station, to the second base station during handover period, and the second base station collects the assignment information, and assigns a radio resource to a mobile terminal existing in its own cell based on the collected radio resource assignment information, so that interference from the first base station is decreased.